The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Many communication standards have been developed to meet the demands for mobile communications. Example communication standards include Global System for Mobile communications (GSM), General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Universal Mobile Telecommunications System (UMTS), Worldwide Interoperability for Microwave Access (WiMAX) technology, and Long Term Evolution (LTE) technology, and the like. When setting up a voice call for a mobile terminal (or sometimes also referred to as a user equipment or UE), some communication standards rely upon circuit-switched networks, and some communication standards rely upon packet-switched networks. A service provider may implement a service network that offers setting up a voice call for a mobile terminal using either a circuit-switched network or a packet-switched network. While setting up a voice call, the service network may first attempt to use the packet-switched network, and may use the circuit-switched network instead when the signal quality between the mobile terminal and the packet-switched network is poor. In some applications according to the LTE standards, changing from the packet-switched network to the circuit-switched network when setting up a call is also known as the Circuit Switched Fallback (CSFB) functionality in the 3rd Generation Partnership Project Technical Specification (3GPP TS) 23.272.